How did speech and language originated in humans? This is one of the most interesting, and still, unanswered questions in evolutionary sciences. Although several disciplines have provided valuable insights into our understanding of the evolution of language, the study of non-human primate vocal communication might provide some very valuable clues about the mechanisms and social conditions associated with the evolution of speech in humans. In many animals, the imitation of calls plays an important role in the formation and maintenance of friendships and other aspects of their social lives. In humans, the ability to imitate others is fundamental during the early stages of life, when infants are learning to speak. Imitative learning also allows us to learn new languages and accents during adulthood. The study of how imitation and learning function in primates can provide important information about how human language could have evolved from a simpler communication system.
In this doctoral dissertation project, the PIs will investigate the acoustic structure and social function of the most common vocalization, known as the neigh, of northern muriqui monkeys (Brachyteles hypoxanthus). The PIs are particularly interested in how the structure of the calls vary between individuals, sexes, and members of different groups, and in how variation in acoustic structure and social functions of the call may be linked. Results from a 2-month pilot study suggest that neigh vocalizations emitted by individuals from adjacent groups are distinctive from each other, and therefore merit much closer analyses. During a 14 month field study at the Biological Station of Caratinga in Minas Gerais, Brazil, the PIs will investigate i) whether female muriquis are able to imitate the vocalizations of novel companions when they transfer into new groups, resulting in distinctive neighs for each group; ii) whether vocalizations can provide information about the caller's sex, or reproductive condition; and iii) whether differences in the number of calls per individual correspond to levels of sociality, with higher number of vocalizations predicted for individuals who maintain a larger number or associates.
Investigating the effect of imitation and social environment on primate vocal structure will provide insights into how humans learn linguistic skills, potentially helping to develop more effective techniques for teaching non-native languages. The collection and analyses of behavioral data and vocal recordings will be conducted by a doctoral student, thereby contributing to NSF's mission of training future scientists and increasing diversity. The study also builds on established long-term, international collaborations with Brazilian researchers and students, and therefore promotes international collaboration. The results from this study will be available through publications in appropriate scientific journals and we will prepare a CD with a selection of vocalizations to be included within the Primate Info. Net. Factsheet System stored at the library of the National Primate Research Center - University of Wisconsin. The PIs will make a special effort to apply our results to advance conservation efforts on behalf of this critically endangered species.
